Reduced iron mass cooling method and cooling device

ABSTRACT

In a method and an apparatus for cooling a reduced-iron agglomerate in a reduced-iron agglomerate production equipment wherein an iron oxide agglomerate is reduced in a reducing furnace and discharged as a reduced-iron agglomerate, a conveyer to convey said reduced-iron agglomerate is installed at the outlet of said reduced-iron agglomerate production equipment, a plurality of spray nozzles are installed above, or above and below, said conveyer at intervals in the conveying direction of said reduced-iron agglomerate, and said reduced-iron agglomerate on said conveyer is cooled intermittently by ejecting cooling water, continuously or intermittently, through said spray nozzles.

[TECHNICAL FIELD]

[0001] The present invention relates to a method and an apparatus forcooling a high-temperature reduced-iron agglomerate that is reduced in,and discharged continuously from, a reducing furnace, in reduced-ironproduction equipment, to produce a reduced-iron agglomerate from an ironoxide agglomerate.

[0002] Here, the above method and apparatus include, for example, amethod and an apparatus for cooling a reduced-iron agglomerate producedin a rotary hearth furnace, for reduction, wherein a reduced iron isproduced by processing dust and sludge containing metallic oxidegenerated in the metal refining industry and the metal processingindustry.

[0003] [BACKGROUND ART]

[0004] As a method for cooling a reduced-iron agglomerate dischargedfrom a reduced-iron production equipment, a method has heretofore beenput into practical use wherein a reduced-iron agglomerate is immersedand cooled in a water bath, thereafter taken out from the water bathwith a conveyer, discharged directly to an earth floor and stored instacks, and then, according to circumstances, conveyed and charged intoan electric arc furnace.

[0005] However, the reduced-iron agglomerate produced by this immersingand cooling method has a high water content and, when it is chargeddirectly into molten metal, there is the danger of a water vaporexplosion. Therefore, it has been used only for charging into anelectric arc furnace. Moreover, the reduced-iron agglomerate has theproblems of pulverization and reoxidation.

[0006] Japanese Patent No. 3145834 discloses a method for producingreduced-iron briquettes wherein reduced iron produced by a directreduction ironmaking method is formed into briquettes by a briquettemachine and the reduced-iron briquettes are cooled slowly, at a coolingrate of 150 to 250° C./min., with a water spray.

[0007] However, this method is a method wherein high-temperaturereduced-iron briquettes are cooled slowly with a water spray in order tosuppress cracking of the reduced-iron briquettes and not a methodwherein a reduced-iron agglomerate discharged from a reduced-ironproduction equipment, such as a rotary hearth furnace, is cooled.Moreover, this method does not take an appropriate water content of thereduced-iron agglomerate into consideration.

[0008] Further, Japanese Patent No. 3009661 discloses a method whereinhigh-temperature reduced-iron briquettes having been heated and reducedare cooled with water so that an average cooling rate may be in therange from 1,500 to 500° C./min. during the time when the surfacetemperature decreases from 650° C. to 150° C.

[0009] However, this method is one that is related to the cooling ofreduced-iron pellets that are different in size and features from anagglomerate such as briquettes as intended in the present invention.Therefore, this method cannot be applied as it is.

[0010] In addition, though the temperature of a reduced-iron agglomeratedischarged from a rotary hearth furnace is about 1,000° C., the patentdescribes neither a cooling method and a cooling rate in the temperatureabove 650° C. nor a concrete cooling means even in the temperature below650° C., and further pays no attention at all to the water content ofagglomerate.

[SUMMARY OF THE INVENTION]

[0011] The object of the present invention is, by solving theaforementioned problems of prior art, to provide a cooling method and acooling apparatus for regulating the temperature at the center, and thewater content, of a reduced-iron agglomerate to appropriate ranges andalso to provide the following concrete means for solving thetechnological problems: to suppress the reoxidation of a reduced-ironagglomerate caused by the atmospheric air by means of rapidly coolingthe reduced-iron agglomerate, at about 1,000° C., discharged from areduced-iron production equipment such as a rotary hearth furnace to atemperature below 300° C.; to make it possible to charge thereduced-iron agglomerate into molten metal, to decrease the waterevaporation energy during melting by means of controlling the watercontent of the reduced-iron agglomerate after the cooling to 6% or less;and to suppress the pulverization and the reoxidation of thereduced-iron agglomerate by means of optimizing a cooling time.

[0012] The present invention solves the aforementioned problems and thegist of the present invention is as follows;

[0013] (1) A method for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

[0014] installing a conveyer to convey said reduced-iron agglomerate atthe outlet of said reduced-iron agglomerate production equipment;

[0015] installing a plurality of spray nozzles above or above and belowsaid conveyer at intervals in the conveying direction of saidreduced-iron agglomerate; and

[0016] cooling said reduced-iron agglomerate on said conveyerintermittently by ejecting cooling water continuously through said spraynozzles.

[0017] (2) A method for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

[0018] installing a conveyer to convey said reduced-iron agglomerate atthe outlet of said reduced-iron agglomerate production equipment;

[0019] installing a plurality of spray nozzles above or above and belowsaid conveyer at intervals in the conveying direction of saidreduced-iron agglomerate; and

[0020] cooling said reduced-iron agglomerate on said conveyerintermittently by ejecting cooling water intermittently through saidspray nozzles so that an ejecting time T1 and an ejection stopping timeT2 may satisfy the following expression (1),

1.2×T1≦T1+T2≦10×T1  (1),

[0021] where, T1 is an ejecting time and T2 an ejection stopping time.

[0022] (3) A method for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

[0023] installing a conveyer to convey said reduced-iron agglomerate atthe outlet of said reduced-iron agglomerate production equipment;

[0024] installing a plurality of spray nozzles above said conveyer;

[0025] spraying cooling water through said spray nozzles on saidreduced-iron agglomerate on said conveyer; and

[0026] accumulating said cooling water so as to form a water layer 1 mmto less than 10 mm, in depth, on said conveyer.

[0027] (4) An apparatus for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

[0028] a conveyer to convey said reduced-iron agglomerate at the outletof said reduced-iron agglomerate production equipment; and

[0029] a plurality of spray nozzles above or above and below saidconveyer at the intervals of P, satisfying the following expression (2),in the conveying direction of said reduced-iron agglomerate in order tocool said reduced-iron agglomerate on said conveyer intermittently byejecting cooling water continuously through said spray nozzles,

1.2×B≦P≦10×B  (2),

[0030] where, B is the spread width of cooling water in the conveyingdirection and P is the intervals of installed spray nozzles.

[0031] (5) An apparatus for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

[0032] a conveyer to convey said reduced-iron agglomerate at the outletof said reduced-iron agglomerate production equipment; and

[0033] a plurality of spray nozzles above or above and below, saidconveyer at intervals in the conveying direction of said reduced-ironagglomerate and setting the spread width of cooling water in theconveying direction B and the spread width thereof in the conveyer widthdirection W so as to satisfy the following expression (3) in order tocool said reduced-iron agglomerate on said conveyer intermittently byejecting said cooling water through said spray nozzles,

W≧2×B  (3),

[0034] where, W is the spread width of cooling water in the conveyerwidth direction and B is the same in the conveying direction.

[0035] (6) An apparatus for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

[0036] a conveyer to convey said reduced-iron agglomerate at the outletof said reduced-iron agglomerate production equipment; and

[0037] a plurality of spray nozzles above, or above and below, saidconveyer at the intervals of P, satisfying the following expression (4),in the conveying direction of said reduced-iron agglomerate in order tocool said reduced-iron agglomerate on said conveyer intermittently byejecting cooling water intermittently through said spray nozzles,

B≦P  (4),

[0038] where, B is the spread width of cooling water in the conveyingdirection and P is the intervals of installed spray nozzles.

[0039] (7) An apparatus for cooling a reduced-iron agglomerate accordingto the item (6), characterized in that said spread width of coolingwater in the conveying direction B and said spread width thereof in theconveyer width direction w satisfy the following expression (3),

W≧2×B  (3),

[0040] where, w is the spread width of cooling water in the conveyerwidth direction and B is the same in the conveying direction.

[0041] (8) An apparatus for cooling a reduced-iron agglomerate accordingto any one of the items (4) to (7), characterized in that said spreadwidth of cooling water in the conveyer width direction W and the widthof said conveyer CW satisfy the following expression (5),

CW≦W  (5),

[0042] where, CW is the width of a conveyer and W is the spread width ofcooling water in the conveyer width direction.

[0043] (9) An apparatus for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

[0044] a conveyer to convey said reduced-iron agglomerate at the outletof said reduced-iron agglomerate production equipment;

[0045] a plurality of spray nozzles to spray cooling water on saidreduced-iron agglomerate above said conveyer; and

[0046] side portions arranged on said conveyer so as to accumulate saidcooling water and form a water layer 1 mm to less than 10 mm, in depth,on said conveyer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047]FIG. 1 is a view showing a cooling apparatus according to thepresent invention.

[0048]FIG. 2 is a plan view taken on line A-A of FIG. 1.

[0049]FIG. 3 is an expanded sectional view being taken on line C-C ofFIG. 2 and showing an example of water spray according to the presentinvention.

[0050]FIG. 4 is a front view taken on line B-B of FIG. 2.

[0051]FIG. 5 is a view showing an example of spray nozzles according tothe present invention.

[0052]FIG. 6 is a graph showing the relationship between the sprayamount of cooling water and the temperature at the center of areduced-iron agglomerate.

[0053]FIG. 7 is a graph showing the relationship between the sprayamount of cooling water and the water content of a reduced-ironagglomerate.

[0054]FIG. 8 is a graph showing the relationship between the temperatureat the center of a reduced-iron agglomerate and the water contentthereof.

[0055]FIG. 9 is a view showing an example of a cooling pattern accordingto the present invention.

[0056]FIG. 10 is a graph showing an example of the temperature change ofagglomerate according to the present invention.

[0057]FIG. 11 is a view showing another cooling apparatus according tothe present invention wherein spray nozzles are installed above andbelow a conveyer.

[0058]FIG. 12 is a view showing a water spraying situation in thecooling apparatus shown in FIG. 11.

[0059]FIG. 13 is a view showing a water supply means in the coolingapparatus shown in FIG. 11.

[0060]FIG. 14 is a view showing a conventional arrangement of spraynozzles.

[0061]FIG. 15 is a view showing another conventional arrangement ofspray nozzles.

[0062]FIG. 16 is a plan view being taken on line A-A of FIG. 1 andshowing another embodiment according to the present invention.

[0063]FIG. 17 is an expanded sectional view being taken on line C-C ofFIG. 2 and showing another example of water spray according to thepresent invention.

[0064]FIG. 18 is a view showing another example of a cooling patternaccording to the present invention.

[0065]FIG. 19 is a view showing another cooling apparatus according tothe present invention.

[0066]FIG. 20 is a view showing the structure of a cooling conveyer.

[0067]FIG. 21 is a graph showing the relationship between the sprayamount of cooling water and the temperature at the center of areduced-iron agglomerate.

[0068]FIG. 22 is a graph showing the relationship between the sprayamount of cooling water and the water content of a reduced-ironagglomerate.

[THE MOST PREFERRED EMBODIMENT]

[0069] 1) The present invention is explained on the basis of the coolingapparatus shown in FIGS. 1 and 2.

[0070] An iron oxide agglomerate is reduced in a rotary hearth furnace13 used as a reducing furnace and the reduced-iron agglomerate thusproduced is discharged continuously from an outlet 8 to discharge thereduced-iron agglomerate. The discharged high-temperature reduced-ironagglomerate 5 is cooled with water sprayed through a plurality of spraynozzles 1 while being conveyed on a conveyer 6 in a cooling apparatus 16placed in connection with the outlet 8, then discharged from anotheroutlet 7 to discharge the reduced-iron agglomerate, and conveyed to astorage installation, or the like, not shown in the figures.

[0071] Each of the spray nozzles 1 is attached at prescribed intervalsto a nozzle header 2 installed in parallel with the conveying directionof, and above, the conveyer 6.

[0072] The spray nozzles 1, the spray header 2 and the conveyer 6 arecovered by a casing 15 and, at the top end of the casing 15, the outlet7 is placed to discharge the cooled reduced-iron agglomerate 5 and, atthe bottom end thereof, the outlet 9 is placed to discharge sludgeformed by spraying water on the reduced-iron agglomerate 5.

[0073]FIG. 2 shows a plan view taken on line A-A of FIG. 1 from abovethe conveyer 6 and the cooling water sprayed through each of the spraynozzles 1 (hereunder referred to as “cooling water” or “spray water” insome cases) is sprayed at intervals so as to form a spread width ofcooling water in the conveying direction “B” as shown by the spray range1-1.

[0074]FIG. 3 is an expanded sectional view taken on line C-C of FIG. 2.In the figure, each of the spray nozzles 1 is attached to the sprayheader 2 at intervals “P” in the conveying direction and spray water issprayed at intervals on the conveyer 6 so as to form the spread width ofcooling water in the conveying direction “B”.

[0075]FIG. 4 shows a front view taken on line B-B of FIG. 2. In thefigure, a spray nozzle 1 is attached to the spray header 2 disposed inthe center of the width direction of the conveyer 6 and spray water issprayed on the conveyer 6 so as to form the spread width in the widthdirection “W” that is larger than the width of the conveyer 6 “CW”.

[0076] Water is supplied to the spray header 2 through a feed water pipe3 as shown in FIG. 5.

[0077] As explained above, a cooling apparatus according to the presentinvention is an apparatus that intermittently cools a reduced-ironagglomerate 5 on a conveyer 6 by installing a plurality of spray nozzles1 above the conveyer 6 at intervals in the conveying direction of thereduced-iron agglomerate 5 and ejecting spray water continuously througheach of the spray nozzles. The condition that assures intermittentcooling is “B<P” as it is understood from FIG. 3.

[0078] By intermittent cooling, the surface temperature of areduced-iron agglomerate 5 on a conveyer 6 lowers while changing forexample as shown in FIG. 10. That is, the surface of the reduced-ironagglomerate is cooled with spray water ejected through the first spraynozzle 1, thereafter the surface temperature begins to rise due to theinternal heat of the reduced-iron agglomerate during the time until thesurface is cooled with the next spray water, and the surface temperaturerise stops at the time when the temperatures at the inside and theoutside of the reduced-iron agglomerate balance with each other.

[0079] Then, next cooling is commenced from the balanced temperaturewith the next spray water. By repeating such steps, the reduced-ironagglomerate 5 is cooled to 100° C. to 300° C. in accordance with such acooling pattern as shown in FIG. 10. In the case of intermittentcooling, since the temperature of a reduced-iron agglomerate 5 lowers bythe giving and receiving of heat in the agglomerate and the forcedcooling with spray water supplied from the outside, the unit consumptionof water can be reduced in comparison with the case of continuous forcedcooling.

[0080] The reason why cooling can be accomplished with a small unitconsumption of water is presumably that the internal transfer of heat ina reduced-iron agglomerate is faster than that in the case of applyingspray water unilaterally from outside.

[0081] Further, in the case of the intermittent cooling of thereduced-iron agglomerate, the water sprayed on the surface thereofevaporates and the surface dries due to the rise of the surfacetemperature between cooling and the subsequent cooling. By repeatingsuch a pattern, the surface of the reduced-iron agglomerate is cooled toa target discharge temperature while water spraying and evaporation arerepeated alternately. By so doing, the reduced-iron agglomerate 5discharged from a cooling apparatus according to the present inventioncan have a water content of 6% or less.

[0082] It is preferable that the water content of a reduced-ironagglomerate is low in order to reduce the energy consumption duringmelting in an electric arc furnace or the like and a preferable watercontent is also 6% or less in order to prevent a water vapor explosionat the time when the reduced-iron agglomerate is charged into moltenmetal.

[0083] A preferable temperature of a reduced-iron agglomerate at thetime of discharge after cooling is in the range from 100° C. to 300° C.in the present invention. A reduced-iron agglomerate discharged from arotary hearth furnace at about 1,000° C. is cooled to a temperature inthe range from 100° C. to 300° C. by intermittent water spray.

[0084] In the general arrangement of cooling nozzles, as shown in FIGS.14 and 15, cone spray nozzles are arranged so that water may be sprayeduniformly over the entire area in the width and conveying directions ofa reduced-iron agglomerate.

[0085] In this arrangement, the temperature difference between theinterior and the surface of a reduced-iron agglomerate (a hightemperature at the interior and a low temperature at the surface)increases due to the continuous water spray and a larger amount of wateris required in comparison with the intermittent water cooling accordingto the present invention. When a water amount is increased in order tocool a reduced-iron agglomerate sufficiently in the interior, waterremains on the surface that has already been cooled to a low temperatureand the water content exceeds 6%.

[0086] Further, when cone spray nozzles are used as shown in FIG. 14 or15, overlaps are formed in the region 1-2 or 1-3 sprayed through eachnozzle, the cooling state varies in the direction of the width of aconveyer, and thus the temperature and the water content of areduced-iron agglomerate also vary.

[0087] The first cooling apparatus according to the present invention isconfigured so that the relation between the spread width of spray waterin the conveying direction “B” and the intervals of installed spraynozzles “P” may satisfy the aforementioned expression (2), namely1.2×B≦P≦10×B.

[0088] The condition “1.2×B≦P” is determined as the condition that makessure that a sprayed range 1-1 is firmly separated from the sprayed rangeof an adjacent spray nozzle 1 as shown in FIG. 2, namely the conditionfor the assurance of intermittent cooling.

[0089] The condition “P≦10×B” is determined as the condition that makessure that the temperature rise caused by the internal heat of areduced-iron agglomerate is not saturated during the time betweencooling and the subsequent cooling and effective cooling is secured.

[0090] Next, the second cooling apparatus according to the presentinvention is configured so that the relation between the spread width ofspray water in the conveying direction “B” and the spread width thereofin the conveyer width direction “W” may satisfy the aforementionedexpression (3), namely W≧2×B.

[0091] Under this condition, by employing, for example, flat spraynozzles that make the sprayed ranges 1-1 flat, the spread width of spraywater in the conveying direction “B” is nearly constant in the conveyerwidth direction, therefore the variation of the cooling state in theconveyer width direction decreases, and resultantly intermittent coolingcan be carried out effectively.

[0092] Further, the first and second cooling apparatuses according tothe present invention are configured so that the relation between thespread width of spray water in the conveyer width direction “W” and thewidth of the conveyer “CW” may satisfy the aforementioned expression(5), namely CW≦W.

[0093] That is, by building up the relation between “W” and “CW” asshown in FIG. 4, it becomes possible to cool a reduced-iron agglomerateon a conveyer 6 uniformly in the conveyer width direction.

[0094] In FIG. 1, a reduced-iron agglomerate 5 discharged from a rotaryhearth furnace 13 is loaded continuously on a conveyer 6 and conveyed.Spray nozzles 1 are arranged above the conveyer 6 at prescribedintervals in the direction of the conveyer traveling.

[0095] As a result, though water is sprayed continuously through each ofthe spray nozzles 1, the water is intermittently sprayed on thereduced-iron agglomerate 5 conveyed continuously on the conveyer 6. Thecooling pattern of intermittent water spray as viewed from agglomerateis, for example, as shown in FIG. 9, and the time durations of “on” and“off” of the water spray can be adjusted by the relation between “P” and“B”.

[0096]FIG. 11 shows another cooling apparatus according to the presentinvention. That is, a high-temperature reduced-iron agglomerate 5reduced in a rotary hearth furnace 13 is fed from an outlet 8 on aconveyer 6 in a cooling apparatus 16 installed in connection with theoutlet, cooled with water sprayed through a plurality of upper spraynozzles 1 and lower spray nozzles la installed above and below theconveyer 6 while being conveyed, and then discharged from a reduced-ironagglomerate outlet 7.

[0097] In this way, a high-temperature reduced-iron agglomerate loadedon a conveyer 6 is cooled from top and bottom by a plurality of nozzles1 and 1 a installed above and below the conveyer 6. By so doing, itbecomes possible to load a reduced-iron agglomerate in plural layers ona conveyer 6 and to improve productivity.

[0098]FIG. 12, like FIG. 4, shows the state of spraying water throughspray nozzles 1 and 1 a installed above and below a conveyer 6 and FIG.13, like FIG. 5, shows means 2, 2 a, 3 and 3 a for supplying water toupper and lower spray nozzles 1 and 1 a.

[0099] As a conveyer 6, a tabular type or a wire-gauze type conveyer isadopted and, in the case where a reduced-iron agglomerate is cooled withnozzles installed above and below a conveyer 6, a cooling efficiencyfurther improves when a wire gauze type conveyer 6 is adopted. Further,with regard to the size of the openings of the wire gauze, any size maybe acceptable, as long as a reduced-iron agglomerate does not fallthrough when it is loaded thereon, but a preferable size of the openingsis about 10 mm.

[0100] Another present invention is explained on the basis of thecooling apparatus shown in FIGS. 1 and 16.

[0101]FIG. 16 shows an example of a plan view taken on line A-A of FIG.1 from above the conveyer 6. In the figure, the intervals “P” of spraynozzles 1 are arranged so that “P” may equal to “B” and water ejectedfrom each of the spray nozzles 1 is sprayed so as to form the spreadwidth in the conveying direction “B” as shown by the spraying range 1 a.This arrangement makes it possible for the spread widths of spray waterin the conveying direction “B” of adjacent nozzles 1 not to overlap witheach other.

[0102]FIG. 17 is an expanded sectional view taken on line C-C of FIG.16. In the figure, each of the spray nozzles 1 is attached to a sprayheader 2 at intervals “P” in the conveying direction and spray water issprayed on a conveyer 6 so as to form the spread width in the conveyingdirection “B”.

[0103] Likewise, FIG. 4 is a front view taken on line B-B of FIG. 16. Inthe figure, a spray nozzle 1 is attached to the spray header 2 disposedin the center of the width direction of the conveyer 6 and spray wateris sprayed on the conveyer 6 so as to form a spread width in the widthdirection “W” that is larger than the width of the conveyer 6 “CW”.

[0104] Water is supplied to a spray header 2 through a feed water pipe 3as shown in FIG. 1.

[0105] In the present invention, as explained above, a plurality ofspray nozzles 1 are installed above a conveyer 6 at prescribed intervalsin the conveying direction, of the reduced-iron agglomerate 5, therelation between an ejecting time “T1” and an ejection stopping time“T2” of each of the spray nozzles 1 is arranged to satisfy theexpression “1.2×T1≦T1+T2≦10×T1” and the reduced-iron agglomerate 5 onthe conveyer is cooled intermittently (on-off) as shown in FIG. 18.

[0106] By employing intermittent cooling, the surface temperature of areduced-iron agglomerate 5 on a conveyer 6 lowers while changing, forexample, as shown in FIG. 10. That is, by ejecting water through spraynozzles 1 for a time “T1” and stopping the water ejection for a time“T2”, the surface temperature of the reduced-iron agglomerate begins torise (heat recovery) due to the internal heat of the reduced-ironagglomerate during the ejection stopping time “T2” after cooled withspray water for the time “T1” and the surface temperature rise stops atthe time when the temperatures at the inside and the outside of thereduced-iron agglomerate balance with each other.

[0107] Then, the next cooling commences, from the balanced temperature,with the next spray water. By repeating such steps, the reduced-ironagglomerate 5 is cooled to 100° C. to 300° C. in accordance with such acooling pattern as shown in FIG. 10. In the case of intermittentcooling, as the temperature of a reduced-iron agglomerate 5 lowers bythe giving and receiving of heat in the agglomerate and the forcedcooling with spray water supplied from the outside, the unit consumptionof water can be reduced in comparison with the case of continuous forcedcooling.

[0108] The reason why cooling can be accomplished with a small unitconsumption of water is presumably that the internal transfer of heat inthe reduced-iron agglomerate is faster than that in the case of applyingspray water unilaterally from outside.

[0109] Further, in the case of the intermittent cooling of thereduced-iron agglomerate, the water sprayed on the surface thereofevaporates and the surface dries due to the rise of the surfacetemperature between one cooling and the subsequent cooling. By repeatingsuch a pattern, the surface of the reduced-iron agglomerate is cooled toa target discharge temperature while water spraying and evaporation arerepeated alternately. By so doing, the reduced-iron agglomerate 5discharged from a cooling apparatus according to the present inventioncan secure a water content of 6% or less.

[0110] It is preferable that the water content of a reduced-ironagglomerate is low in order to reduce the energy consumption duringmelting in an electric arc furnace, or the like, and a preferable watercontent is also 6% or less in order to prevent water vapor explosion atthe time when the reduced-iron agglomerate is charged into molten metal.

[0111] As shown in FIGS. 14 and 15, cone spray nozzles are generallyused as cooling nozzles and arranged so that the spread of spray waterejected through the cooling nozzles may interfere with each other overthe entire area in the width and conveying directions of a reduced-ironagglomerate and thus the spray water may be sprayed on over all thereduced-iron agglomerate.

[0112] In this arrangement, the temperature difference between theinterior and the surface of a reduced-iron agglomerate (a hightemperature at the interior and a low temperature at the surface)increases due to the continuous water spray and a larger amount of wateris required in comparison with the intermittent water cooling accordingto the present invention. When a water amount is increased in order tocool a reduced-iron agglomerate sufficiently up to the interior, waterremains on the surface that has already been cooled to a low temperatureand the water content exceeds 6%.

[0113] Further, when cone spray nozzles are used as shown in FIG. 14 or15, overlaps are formed in the region 1-2 or 1-3 sprayed through eachnozzle, the cooling state varies in the direction of the width of aconveyer, and thus the temperature and the water content of areduced-iron agglomerate also vary.

[0114] Another cooling apparatus according to the present invention isconfigured so that the relation between an ejecting time “T1” and anejection stopping time “T2” of spray water may satisfy the expression

1.2×T1≦T1+T2≦10×T1.

[0115] That is, the term “1.2×T1≦T1+T2” is the condition for securingintermittent cooling for a shortest time period in order to determine anejecting time and an ejection stopping time of spray water.

[0116] The term “T1+T2≦10×T1” is the condition for securing effectivecooling without the saturation of a temperature rise caused by theinternal heat of a reduced-iron agglomerate after cooling.

[0117] The third cooling apparatus according to the present invention isconfigured so that the spread width of spray water in the conveyingdirection “B” and the intervals of spray nozzles in the conveyingdirection “P” may satisfy the expression “B≦P”. The condition determinesthe intervals of spray nozzles 1 so that the spread widths of spraywater “B” ejected through the spray nozzles 1 may not overlap with eachother and, under this condition, uniform cooling is realized.

[0118] The fourth cooling apparatus according to the present inventionis configured so that the relation between the spread width of spraywater in the conveyer width direction “W” and the spread width thereofin the conveying direction “B” may satisfy the expression “2B≦W”. Underthe condition, a spray region la becomes flat as shown in FIG. 16.

[0119] For example, when flat spray nozzles are adopted, as the spreadwidth of spray water in the conveying direction “B” becomes nearlyconstant in the conveyer width direction, the variation of the coolingstate in the conveyer width direction decreases and resultantlyintermittent cooling can be carried out effectively.

[0120] Further, in the aforementioned third cooling apparatus accordingto the present invention, by configuring the cooling apparatus so thatthe relation between the spread width of spray water in the conveyerwidth direction “W” and the conveyer width “CW” may satisfy theexpression “CW≦W”, namely by building up the relation between “W” and“CW” as shown in FIG. 4, a reduced-iron agglomerate on a conveyer 6 iscooled uniformly in the conveyer width direction.

[0121] [Examples]

[0122] Next, the results obtained from the examples of the presentinvention are shown in FIGS. 6 to 8.

[0123] The intermittent cooling of the invention examples was performedunder the condition prepared so that the relation between the spreadwidth of spray water in the conveying direction “B” and the intervals ofthe installed spray nozzles “P” might satisfy the expression “2B=P” andunder this condition prepared so that the relation between the spreadwidth of spray water in the conveying direction “B” and the intervals ofthe installed spray nozzles “P” might satisfy the expression “B≦P” andthe relation between the spraying time and the spray stopping time mightsatisfy the expression “1.2×T1+T2”. The continuous cooling of thecomparative examples was performed under the condition of “B ≧P”.

[0124]FIG. 6 shows the relationship between the temperature at thecenter of a reduced-iron agglomerate during cooling and a spray wateramount. It is understood that the intermittent cooling of the inventionexample is excellent in cooling effect in comparison with the continuouscooling of the comparative example.

[0125] By the present invention, the temperature at the center of thereduced-iron agglomerate is lowered to preferably not higher than 300°C., as shown by the solid line, and still more preferably not higherthan 200° C., as shown by the broken line.

[0126] Further, whereas, in the case of the intermittent cooling of theinvention example, the temperature is 300° C. or lower when the relativespray water amount is 0.7 or more, in the case of the continuous coolingof the comparative example, the relative spray water amount of 2.0 isrequired.

[0127]FIG. 7 shows the relationship between a spray water amount and awater content after cooling. In the case of the intermittent coolingaccording to the present invention, it is possible to regulate the watercontent of a reduced-iron agglomerate by the spray water amount. Apreferable water content is not more than 6% as shown by the solid lineand still more preferably not more than 5%, as shown by the broken line.

[0128] In the case of the intermittent cooling of the invention example,the water content is 6% or less when the relative spray water amount is1.3 or less and the temperature is 300° C. or lower and the watercontent is 6% or less when the relative spray water amount is in therange from 0.7 to 1.3. On the other hand, in the case of the continuouscooling of the comparative example, the water content exceeds 6% whenthe temperature is controlled to 300° C. or lower.

[0129]FIG. 8 is a graph obtained by putting FIGS. 6 and 7 together andshows the relationship between the temperature at the center of areduced-iron agglomerate and the water content thereof. In the case ofthe continuous cooling of the comparative example, the water contentexceeds 6% when the temperature at the center of the reduced-ironagglomerate is lowered to 300° C. or lower and the temperature at thecenter exceeds 300° C. when the water content is controlled to 6% orless.

[0130] In contrast, in the case of the intermittent cooling of theinvention example, as shown by the solid line, the temperature at thecenter and the water content can be regulated to 300° C. or lower and 6%or less respectively and a good reduced-iron agglomerate can beobtained.

[0131] 2) Another present invention is further explained on the basis ofthe cooling apparatus shown in FIG. 19.

[0132] The technological concept of the present invention is explainedhereunder.

[0133] Spray nozzles are arranged above a cooling conveyer along theconveying direction and a reduced-iron agglomerate is cooled with watersprayed from above. However, the bottom surface and the center portionof the reduced-iron agglomerate are hardly cooled with only the coolingfrom above.

[0134] Therefore, the temperature difference appears between the top andbottom surfaces of the reduced-iron agglomerate and, when a spray wateramount is insufficient, the heat at the bottom surface is transferredafter cooling and the cooling becomes insufficient.

[0135] On the other hand, when a spray water amount is abundant, waterpenetrates the top surface of a low temperature and the water contentincreases.

[0136] In this light, with intent to achieve both “cooling to atemperature of 300° C. or lower at the center” and “a water content of6% or less” at the same time, the method is used wherein a reduced-ironagglomerate is cooled from the top and bottom surfaces by raising boththe side portions of a conveyer and accumulating cooling water so as toform a water layer 1 mm to less than 10 mm on the conveyer.

[0137] When water accumulates so as to form a water layer 1 to less than10 mm (which corresponds to less than a half of the thickness of areduced-iron agglomerate) at the bottom of a conveyer by raising boththe side portions of the conveyer, the bottom surface of thereduced-iron agglomerate is cooled by the heat of the evaporation ofwater and the temperature difference between the top and bottom surfacesdecreases. Therefore, both “cooling to a temperature of 300° C. or lowerat the center” and “a water content of 6% or less” can be achieved atthe same time.

[0138] When a water layer at the bottom of a conveyer is less than 1 mmin thickness, the ability to cool the reduced-iron agglomerate isinsufficient. On the other hand, when it is 10 mm or more in thickness,a water content increases excessively. For that reason, the thickness ofa water layer is determined to be in the range from 1 mm to less than 10mm.

[0139] With regard to a method of spraying cooling water on areduced-iron agglomerate through spray nozzles installed above aconveyer, the cooling water may be sprayed intermittently, instead ofcontinuously, on the reduced-iron agglomerate. By this intermittentcooling, it becomes possible to cool a reduced-iron agglomerate to auniform temperature from the surface to the center. The method ofintermittent spraying is not particularly specified and it is preferableto repeat spraying and non-spraying during the course of cooling byadjusting the arrangement and the spread angle of spray nozzles.

[0140] The present invention is explained on the basis of FIGS. 19 and20.

[0141]FIG. 19 shows the overall view of a cooling apparatus according tothe present invention.

[0142] A high-temperature reduced-iron agglomerate is discharged fromthe outlet 8 of a rotary hearth of a reduced-iron production equipmentand loaded on a cooling conveyer 6. The temperature of the reduced-ironagglomerate discharged from the outlet 8 of the rotary hearth is 1,000°C. Spray nozzles 1 are installed above the cooling conveyer 6 andcooling water is sprayed on the reduced-iron agglomerate on the coolingconveyer 6 through the spray nozzles 1.

[0143] In such a cooling apparatus, when the length of the coolingconveyer 6 is set at 6.5 m and the conveying speed at 6.5 m/min., thereduced-iron agglomerate is cooled for about 1 min. In the meantime, thereduced-iron agglomerate is cooled from about 1,000° C. to 300° C. orlower.

[0144] The cooled reduced-iron agglomerate is conveyed from the end ofthe cooling conveyer 6 as a product. Further, sludge formed during thecourse of cooling is separated from water at a shoot 18, thereafterrecovered with a sludge recovery conveyer 17, and reused as an ironsource. Here, vapor generated during the course of cooling is dischargedoutside through a vapor duct 4.

[0145]FIG. 20 shows the structure of a cooling conveyer 6. “W” in theFIG. 20 shows the width direction of the cooling conveyer 6 and “L” thelength direction thereof. FIG. 20 shows a pallet of the cooling conveyer6 and the cooling conveyer 6 is composed of a series of the pallets inthe length direction.

[0146] Such side walls as shown in FIG. 20 are placed at both the sidesof the cooling conveyer 6 and the structure is configured so thatcooling water sprayed through spray nozzles 1 may not fall down from thesides of the cooling conveyer 6. Accordingly, a water layer 1 mm to notmore than 10 mm, in depth, can accumulate at the bottom of the coolingconveyer 6.

[0147] Further, the bottom plate 21 of the cooling conveyer 6 is made ofa steel plate and the structure is configured so that the cooling watermay not fall down from the bottom plate 21.

[0148] [Examples]

[0149] The results of the examples according to the present inventionare shown in FIGS. 21 and 22.

[0150]FIG. 21 is a graph showing the relationship between the sprayamount of cooling water and the temperature at the center of areduced-iron agglomerate. The line indicated as the water depth of 2 mmrepresents the case where the bottom plate 21 of the cooling conveyer 6is made of a steel plate and the line indicated as wire gauze (0 mm)represents the case where the bottom plate of the cooling conveyer 6 ismade of wire gauze. A spray water amount is expressed by a relativevalue obtained by regarding the calculated spray water amount requiredfor cooling as 1.0.

[0151] As shown in FIG. 21, according to this example, in the case ofusing a steel plate as the bottom plate of the cooling conveyer 6 andforming a water layer 2 mm in depth, the temperature at the center of areduced-iron agglomerate can be lowered to 300° C. or lower when thespray water amount is about 1.1 times the calculated required amount.

[0152] On the other hand, in the case of using wire gauze as the bottomplate of the cooling conveyer 6, the temperature at the center of areduced-iron agglomerate can be lowered only to 470° C. even when thespray water amount is about 1.1 times the calculated required amount.

[0153]FIG. 22 is a graph showing the relationship between the sprayamount of cooling water and the water content of a reduced-ironagglomerate. The viewpoint of the figure is the same as that of FIG. 21.

[0154] As shown in FIG. 22, according to this example, in the case ofusing a steel plate as the bottom plate of the cooling conveyer 6 andforming a water layer 2 mm in depth, the water content can be suppressedto 6% or less even when the spray water amount is increased to 1.5 timesthe calculated required amount.

[0155] On the other hand, in the case of using wire gauze as the bottomplate of the cooling conveyer 6, the water content exceeds 6% when thespray water amount exceeds the calculated required amount.

[0156] From the results shown in FIGS. 21 and 22, it can be understoodthat it becomes possible that a temperature at the center of areduced-iron agglomerate is 300° C. or lower and a water content is 6%or less by raising both the side portions of a cooling conveyer 6, usinga steel plate as the bottom plate of the cooling conveyer 6 and forminga water layer 2 mm in depth.

[0157] [Industrial Applicability]

[0158] By a method and an apparatus according to the present invention,it is possible to cool a high-temperature reduced-iron agglomerateintermittently, to cool it effectively to a temperature in the rangefrom 100° C. to 300° C. at a breath and, as a result, to suppress thereoxidation caused by the atmospheric air.

[0159] Further, it is possible to regulate the water content of a cooledreduced-iron agglomerate to 6% or lower, to eliminate the danger of awater-vapor explosion at the time when the reduced-iron agglomerate ischarged into molten metal, and also to suppress the energy required formelting.

[0160] Further, the present invention makes it possible to reduce awater content to 6% or less in comparison with an immersion coolingmethod and therefore to suppress the pulverization and the reoxidation.Furthermore, by the present invention, a conveyer itself is also cooledand, therefore, the durability of the conveyer is improved.

1. A method for cooling a reduced-iron agglomerate in a reduced-ironagglomerate production equipment wherein an iron oxide agglomerate isreduced in a reducing furnace and discharged as a reduced-ironagglomerate characterized by: installing a conveyer to convey saidreduced-iron agglomerate at the outlet of said reduced-iron agglomerateproduction equipment; installing a plurality of spray nozzles above orabove and below said conveyer at intervals in the conveying direction ofsaid reduced-iron agglomerate; and cooling said reduced-iron agglomerateon said conveyer intermittently by ejecting cooling water continuouslythrough said spray nozzles.
 2. A method for cooling a reduced-ironagglomerate in a reduced-iron agglomerate production equipment whereinan iron oxide agglomerate is reduced in a reducing furnace anddischarged as a reduced-iron agglomerate characterized by: installing aconveyer to convey said reduced-iron agglomerate at the outlet of saidreduced-iron agglomerate production equipment; installing a plurality ofspray nozzles above or above and below said conveyer at intervals in theconveying direction of said reduced-iron agglomerate; and cooling saidreduced-iron agglomerate on said conveyer intermittently by ejectingcooling water intermittently through said spray nozzles so that anejecting time T1 and an ejection stopping time T2 may satisfy thefollowing expression (1), 1.2×T1≦T1+T2≦10×T1  (1), where, T1 is anejecting time and T2 an ejection stopping time.
 3. A method for coolinga reduced-iron agglomerate in a reduced-iron agglomerate productionequipment wherein an iron oxide agglomerate is reduced in a reducingfurnace and discharged as a reduced-iron agglomerate characterized by:installing a conveyer to convey said reduced-iron agglomerate at theoutlet of said reduced-iron agglomerate production equipment; installinga plurality of spray nozzles above said conveyer; spraying cooling waterthrough said spray nozzles on said reduced-iron agglomerate on saidconveyer; and accumulating said cooling water so as to form a waterlayer 1 mm to less than 10 mm, in depth, on said conveyer.
 4. Anapparatus for cooling a reduced-iron agglomerate in a reduced-ironagglomerate production equipment wherein an iron oxide agglomerate isreduced in a reducing furnace and discharged as a reduced-ironagglomerate characterized by: a conveyer to convey said reduced-ironagglomerate at the outlet of said reduced-iron agglomerate productionequipment; and a plurality of spray nozzles above or above and belowsaid conveyer at the intervals of P, satisfying the following expression(2), in the conveying direction of said reduced-iron agglomerate inorder to cool said reduced-iron agglomerate on said conveyerintermittently by ejecting cooling water continuously through said spraynozzles, 1.2×B≦P≦10×B  (2), where, B is the spread width of coolingwater in the conveying direction and P is the intervals of installedspray nozzles.
 5. An apparatus for cooling a reduced-iron agglomerate ina reduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by: a conveyer to convey saidreduced-iron agglomerate at the outlet of said reduced-iron agglomerateproduction equipment; and a plurality of spray nozzles above, or aboveand below, said conveyer at intervals in the conveying direction of saidreduced-iron agglomerate and setting the spread width of cooling waterin the conveying direction B and the spread width thereof in theconveyer width direction W so as to satisfy the following expression (3)in order to cool said reduced-iron agglomerate on said conveyerintermittently by ejecting said cooling water continuously through saidspray nozzles, W≧2×B  (3), where, W is the spread width of cooling waterin the conveyer width direction and B is the same in the conveyingdirection.
 6. An apparatus for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by: a conveyer to convey saidreduced-iron agglomerate at the outlet of said reduced-iron agglomerateproduction equipment; and a plurality of spray nozzles above, or aboveand below, said conveyer at the intervals of P, satisfying the followingexpression (4), in the conveying direction of said reduced-ironagglomerate in order to cool said reduced-iron agglomerate on saidconveyer intermittently by ejecting cooling water intermittently throughsaid spray nozzles, B≦P  (4), where, B is the spread width of coolingwater in the conveying direction and P is the intervals of installedspray nozzles.
 7. An apparatus for cooling a reduced-iron agglomerateaccording to claim 6, characterized in that said spread width of coolingwater in the conveying direction B and said spread width thereof in theconveyer width direction W satisfy the following expression (3),W≦2×B  (3), where, W is the spread width of cooling water in theconveyer width direction and B is the same in the conveying direction.8. An apparatus for cooling a reduced-iron agglomerate according to anyone of claims 4 to 7, characterized in that said spread width of coolingwater in the conveyer width direction W and the width of said conveyerCW satisfy the following expression (5), CW≦W  (5), where, CW is thewidth of a conveyer and W is the spread width of cooling water in theconveyer width direction.
 9. An apparatus for cooling a reduced-ironagglomerate in a reduced-iron agglomerate production equipment whereinan iron oxide agglomerate is reduced in a reducing furnace anddischarged as a reduced-iron agglomerate characterized by: a conveyer toconvey said reduced-iron agglomerate at the outlet of said reduced-ironagglomerate production equipment; a plurality of spray nozzles to spraycooling water on said reduced-iron agglomerate above said conveyer; andside portions arranged on said conveyer so as to accumulate said coolingwater and form a water layer 1 mm to less than 10 mm, in depth, on saidconveyer.